Electrochemical intercalation of lithium into graphite was investigated in trimethyl-n-hexylammonium bis(trifluoromethanesulfone) imide (TMHATFSI) room-temperature molten salt containing both lithium bis(trifluoromethanesulfone) imide (LiTFSI) and ethylene carbonate (EC). The electrochemical intercalation of the organic cations into graphite occurred in TMHATFSI molten salt regardless of the presence of LiTFSI. The addition of EC to TMHATFSI molten salt with LiTFSI resulted in the electrochemical formation of the graphite intercalation compound of lithium, probably accompanied by the formation of a solid-electrolyte interface film, which prevents the intercalation of the organic cations. (C) 2003 The Electrochemical Society.